Communicating design ideas is one of the most important skills that a designer or information architect can have. Lets face it, to be a good designer, you also have to be a good seller. You could have the best concept in the world, but unless you can clearly articulate why its the best concept in the world to your stakeholders, it will never see the light of day.
For most of us, these skills don't come naturally...they are developed from experience and discipline. Here are a few tips that can help you develop these skills (with a few excerpts taken from the Cooper newsletter)
Have a good story to tell

Human beings think in stories, and contextualizing the proposed design solution with a story helps your collaborators imagine what the eventual user experience will be like.

Only put as much detail into the design as the idea or concept allows.

It is harder for people to evaluate high-level concepts when their eyes and attention are drawn to the multitude of details. It helps to use Lorem Ipsum for your text, a low fidelity sketch via Visio or PowerPoint, and fake data. This helps people only focus on what's important to you. Make sure to constantly stress that its a "high-level concept" to keep people thinking the same way about it as you did when you created it.

Get all the decision-makers together in the same room

I cant stress how important this one is. Walking a design around to different stakeholders individually will get you completely different results than if everyone is in the same room together...normally causing endless tweaks to your design. Unless everyone can be there, I would highly recommend you re-schedule for a time that works for everyone. Though it may delay approval a bit, it will save you time and decrease iterations.

Carve out time in the schedule for design communication

Communicating design does take time, no doubt about it. But it will save a lot more time by reducing the thrash that occurs when developers don't have a clear understanding about what it is they are supposed to build. Get developers involved early in the design process...their input is invaluable.